Properties of diamond-like carbon nano-coating deposited with RF PECVD method on UV-induced long-period fibre gratings

摘要

The paper discusses the properties of diamond-like carbon (DLC) thin overlays deposited with radio frequency plasma-enhanced chemical vapour deposition (RF PECVD) method on optical fibres with long-period fibre gratings (LPFGs) induced by UV irradiation. In consequence of low deposition temperature, the UV-induced LPFGs can be coated with DLC without damaging the thermally-instable grating structure. We have found that properties of the DLC overlays highly depend on a distance between the LPFG and electrode in the deposition chamber. Moreover, the response of the LPFG to variation in external refractive index (RI) can be tuned by deposition of DLC nano-overlay. For the investigated DLC-coated LPFGs we obtained sensitivity reaching over 3000 nm per RI unit in the range of n_D= 1.33 to 1.37 RIU, which is almost 12 fold higher than for the LPFGs with no overlay in the same RI range.